package suanfa;

import java.util.LinkedList;
import java.util.Queue;

public class maxAreaOfIsland {
    int[] dx={0,0,1,-1};
    int[] dy={1,-1,0,0};
    boolean[][] vis=new boolean[51][51];
    int m,n;
    public int maxAreaOfIsland(int[][] grid) {
        m=grid.length;n=grid[0].length;
        int ret=0;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(grid[i][j]==1 && !vis[i][j]){
                    ret=Math.max(bfs(grid,i,j),ret);
                }
            }
        }
        return ret;
    }
    public int bfs(int[][] grid,int i,int j){
        int count=0;
        Queue<int[]> q=new LinkedList<>();
        q.offer(new int[]{i,j});
        vis[i][j]=true;
        count++;
        while(!q.isEmpty()){
            int[] t=q.poll();
            int a=t[0],b=t[1];
            for(int k=0;k<4;k++){
                int x=a+dx[k],y=b+dy[k];
                if(x>=0&&x<m&&y>=0&&y<n&&grid[x][y]==1&&!vis[x][y]){
                    q.offer(new int[]{x,y});
                    vis[x][y]=true;
                    count++;
                }
            }
        }
        return count;
    }
}
